diff --git a/examples/todoapp/templates.xml b/examples/todoapp/templates.xml
index 254c9532..dd444b50 100644
--- a/examples/todoapp/templates.xml
+++ b/examples/todoapp/templates.xml
@@ -27,13 +27,13 @@
             </span>
             <ul class="filters">
                 <li>
-                    <a href="#/all" t-on-click="updateState({filter:'all'})" t-att-class="state.filter === 'all' ? 'selected' : ''">All</a>
+                    <a href="#/all" t-on-click="updateState({filter:'all'})" t-att-class="{selected: state.filter === 'all'}">All</a>
                 </li>
                 <li>
-                    <a href="#/active" t-on-click="updateState({filter:'active'})" t-att-class="state.filter === 'active' ? 'selected' : ''">Active</a>
+                    <a href="#/active" t-on-click="updateState({filter:'active'})" t-att-class="{selected: state.filter === 'active'}">Active</a>
                 </li>
                 <li>
-                    <a href="#/completed" t-on-click="updateState({filter:'completed'})" t-att-class="state.filter === 'completed' ? 'selected' : ''">Completed</a>
+                    <a href="#/completed" t-on-click="updateState({filter:'completed'})" t-att-class="{selected: state.filter === 'completed'}">Completed</a>
                 </li>
             </ul>
             <button class="clear-completed" t-if="todos.length gt remaining" t-on-click="clearCompleted">
@@ -42,7 +42,7 @@
         </footer>
     </section>
 
-    <li t-name="todoitem" class="todo" t-att-class="(props.completed ? 'completed ' : ' ') + (state.isEditing ? 'editing' : '')">
+    <li t-name="todoitem" class="todo" t-att-class="{completed: props.completed, editing: state.isEditing}">
         <div class="view">
             <input class="toggle" type="checkbox" t-on-change="toggleTodo" t-att-checked="props.completed"/>
             <label t-on-dblclick="editTodo">
diff --git a/src/qweb.ts b/src/qweb.ts
index 17e24ebc..1fa67d21 100644
--- a/src/qweb.ts
+++ b/src/qweb.ts
@@ -162,6 +162,15 @@ export class QWeb {
       const temp = document.createElement("template");
       temp.innerHTML = str;
       return temp.content;
+    },
+    objectToAttrString(obj: Object): string {
+      let classes: string[] = [];
+      for (let k in obj) {
+        if (obj[k]) {
+          classes.push(k);
+        }
+      }
+      return classes.join(" ");
     }
   };
 
@@ -470,6 +479,12 @@ export class QWeb {
       if (name.startsWith("t-att-")) {
         let attName = name.slice(6);
         let formattedValue = this._formatExpression(ctx.getValue(value!), ctx);
+        if (
+          formattedValue[0] === "{" &&
+          formattedValue[formattedValue.length - 1] === "}"
+        ) {
+          formattedValue = `this.utils.objectToAttrString(${formattedValue})`;
+        }
         const attID = ctx.generateID();
         if (!attName.match(/^[a-zA-Z]+$/)) {
           // attribute contains 'non letters' => we want to quote it
@@ -482,6 +497,10 @@ export class QWeb {
           const attValueID = ctx.generateID();
           ctx.addLine(`let _${attValueID} = ${formattedValue};`);
           formattedValue = `'${attValue}' + (_${attValueID} ? ' ' + _${attValueID} : '')`;
+          const attrIndex = attrs.findIndex(att =>
+            att.startsWith(attName + ":")
+          );
+          attrs.splice(attrIndex, 1);
         }
         ctx.addLine(`let _${attID} = ${formattedValue};`);
         attrs.push(`${attName}: _${attID}`);
diff --git a/tests/__snapshots__/qweb.test.ts.snap b/tests/__snapshots__/qweb.test.ts.snap
index 73bc86e9..8da0137c 100644
--- a/tests/__snapshots__/qweb.test.ts.snap
+++ b/tests/__snapshots__/qweb.test.ts.snap
@@ -188,7 +188,20 @@ exports[`attributes t-att-class and class should combine together 1`] = `
     let _1 = 'hello';
     let _3 = context['value'];
     let _2 = 'hello' + (_3 ? ' ' + _3 : '');
-    let c4 = [], p4 = {key:4,attrs:{class: _1,class: _2}};
+    let c4 = [], p4 = {key:4,attrs:{class: _2}};
+    let vn4 = h('div', p4, c4);
+    return vn4;
+}"
+`;
+
+exports[`attributes t-att-class with object 1`] = `
+"function anonymous(context,extra
+) {
+    let h = this.utils.h;
+    let _1 = 'static';
+    let _3 = this.utils.objectToAttrString({a: context['b'],c: context['d'],e: context['f']});
+    let _2 = 'static' + (_3 ? ' ' + _3 : '');
+    let c4 = [], p4 = {key:4,attrs:{class: _2}};
     let vn4 = h('div', p4, c4);
     return vn4;
 }"
diff --git a/tests/qweb.test.ts b/tests/qweb.test.ts
index 12d05837..64041d63 100644
--- a/tests/qweb.test.ts
+++ b/tests/qweb.test.ts
@@ -464,6 +464,15 @@ describe("attributes", () => {
     const result = renderToString(qweb, "test", { value: "world" });
     expect(result).toBe(`<div class="hello world"></div>`);
   });
+
+  test("t-att-class with object", () => {
+    qweb.addTemplate(
+      "test",
+      `<div class="static" t-att-class="{a: b, c: d, e: f}"/>`
+    );
+    const result = renderToString(qweb, "test", { b: true, d: false, f: true });
+    expect(result).toBe(`<div class="static a e"></div>`);
+  });
 });
 
 describe("t-call (template calling", () => {